Motion picture projection system

ABSTRACT

A continuously rewinding motion picture projection system in which a pair of lengths of motion picture film, which define first and second halves of a film program, are arranged in reciprocal head-to-tail relation and are transferred simultaneously back-and-forth between a pair of reels upon which the film lengths are wound in bifilar fashion. Between the reels the film lengths each pass through a projection station which includes a projection lens system directed to a display screen common to both film lengths. The projection station is operable to project upon the display screen film information carried by the film length which, at that time, moves in a forward mode through the projection station. The film lengths are in the same state at the completion of display of the program as they were when the program display was commenced.

United States Patent Inventor Patrick Michael Powers Arcadia, Calif.

Appl. No. 795,846

Filed Feb. 3, 1969 Patented Nov. 2, 1971 Assignee Bell & Howell CompanyPasadena, Calif.

MOTION PICTURE PROJECTION SYSTEM 3,423,152 1/1969 Chaplais ABSTRACT: Acontinuously rewinding motion picture projection system in which a pairof lengths of motion picture film, which define first and second halvesof a film program, are arranged in reciprocal head-to tail relation andare transferred simultaneously back-and-forth between a pair of reelsupon which the film lengths are wound in bifilar fashion. Between thereels the film lengths each pass through a projection station whichincludes a projection lens system directed to a display screen common toboth film lengths. The projection station is operable to project uponthe display screen film information carried by the film length which, atthat time, moves in a forward mode through the projection station. The

film lengths are in the same state at the completion of displayPATENTEUNUV 2 I971 SHEET 3 [IF 5 MOTION PICTURE PROJECTION SYSTEMBACKGROUND OF THE INVENTION 1. Field of the Invention This inventionpertains to motion picture projection systems. More particularly, itpertains to a continuously rewinding system in which a pair of filmlengths, arranged in reciprocal head-to-tail fashion, are shuttledthrough a projection station between a pair of supply/takeup reels wherethe lengths are wound in bifilar manner.

2. Review of the Prior Art Motion picture entertainment of passengersaboard the aircraft of domestic and international air carriers isbecoming commonplace. The presence of such entertainment, and the appealthereof to individual passengers, may become a determinative factor inthe choice by a passenger of which carrier to patronize. Also to beconsidered is the economic burden placed on the carrier by the cost ofservicing the film entertainment system.

International air carriers cannot readily afford the economic burdenassociated with film entertainment systems which require servicing,typically rewinding of the film, at the completion of each showing ofthe film program. Servicing of the system requires the talents ofskilled personnel which either are not available to internationalcarriers at all desired geographic locations or are available in remotelocations only at premium wages. Therefore, especially with respect tointernational carriers, it is desirable to provide film entertainmentsystems which require minimum servicing. Servicing requirements of filmentertainment systems can be reduced significantly by the provisionofsystems in which film is effectively rewound automatically as the filmprogram is presented; in systems with such capability, the "programturnaround time" is effectively zero.

One prior solution to the problem of program turnaround time" isillustrated in U.S. Pat. No. 3,375,054; this patent does not pertainexpressly to airline film entertainment systems, but it does illustratethe way film is handled in current airline systems having zero effectiveprogram turnaround time. According to thedisclosures of this patent, theentertainment system includes only a single reel upon which a continuousstrip of film is coiled. Film is extracted from the center of the coil,led through a projection station, and returned to the outside of thecoil. In such an arrangement, it is apparent that a given frame of filmgradually moves from the outside of the coil slowly along an extensivespiral path to the inside of the coil, and that at the inside of thecoil the film carrying such frame is moved laterally relative to thefilm defining the next outward turn in the coil as the film is extractedfrom the coil. Therefore, it is further apparent that the film slides onitself in moving from the outside to the inside of the reel coil. Duringsuch sliding movement, the film may become scratched so badly that thefilm rapidly becomes noticeably degraded, in terms of the imageprojected, unless dust and dirt are carefully eliminated from the reelarea; dust and dirt control devices add to the cost of such filmentertainment systems. Further, continuous film systems of the typeillustrated in U.S. Pat. No. 3,375,054 presently can be made to operatesuccessfully only with limited quantities of film. Also, filmlubrication is difficult to maintain at levels adequate to keep filmtension levels below those productive of film breakage. Further, in sucharrangements the film tension level often becomes so great at the centerof the film coil that the film pops off the core upon which the film iswound, thereby rendering the system inoperable.

US, Pat. Nos. 1,479,078 and 1,843,650 describe motion picture projectionsystems which have zero or near zero program turnaround time. Thesepatents both describe projection systems in which two separate filmlengths, defining serial portions of a film program, each has its ownseparate supply and takeup reels; that is, both systems use four reelsand two film lengths. The reels are disposed in coaxial pairs, the reelsin each pair being driven in opposite directions so that one film lengthmoves in a forward mode between its reels while the other moves in areverse mode between its reels. Each film length passes through its ownprojector mechanism. Thus, while one film is being displayed, the otheris being rewound. In order that such systems may be useful, both reelsin each coaxial pair must be rotated at the same angular velocity.

The projection systems described in U.S. Pat. Nos. 1,479,078 and1,843,650 require the handling of multiple reels of film, are bulky, andinvolve complex mechanisms and mechanical interlocks. More importantly,these systems are sensitive to thickness differences between the twofilm lengths. As noted, the coaxial reels in the systems are positivelydriven at equal rates. Thus, if one film is thicker than the other, suchfilm will be reeled on its takeup reel faster than the other film, andthe difference in reeling rates will increase as the film on the takeupreel increases. Therefore, if any significant quantities of film areused in these systems, complex control mechanisms must be used, wherethe films are not of equal thickness, to prevent such differentialreeling rates, or else the tension level in the thicker film willrapidly develop to a value adequate to break the film.

U.S. Pat. No. 1,801,061 describes the provision of two films disposed inreciprocal head-to-tail relation on four reels arranged in two coaxialpairs of reels such that one film is being rewound upon its supply reelwhile the other is being moved to its takeup reel; all four reels aredisposed in a housing which must be manually turned end for end relativeto a single projection mechanism. This arrangement also suffers from thesame disadvantages of bulkiness and film thickness sensitivity as thearrangements reviewed immediately above. The requirement for manualhandling is a major element of the problem which this inventionovercomes.

U.S. Pat. Nos. 1,253,796 and 1,893,698 describe bifilar winding upon asupply reel of two unexposed lengths of film, each of which bears acolor-sensitive emulsion layer different from the emulsion layer borneby the other film. These patents describe motion picture cameras ratherthan projection systems, and to the extent these patents pertain toprojection systems they describe simultaneous display of both filmswhich are simultaneously moved in a forward mode through an appropriateprojection mechanism. These arrangements do not purport to solve, and donot suggest a solution to the problem of a motion picture projectionsystem having zero program turnaround time.

U.S. Pat. Nos. 3,240,329 and 3,378,328 described bifilar winding upon apair of reels of a film and a magnetic sound tape defining,respectively, the visual and audio aspects of a composite presentation.The film and the tape are moved simultaneously in a forward mode throughseparate playback devices. This arrangement also makes no contributionto the problem of zero program turnaround time for motion picturedisplays.

Relative to magnetic sound recordings, it is known to record two tracksof stereo sound information in one direction on a length of magneticrecording tape, and to record two additional stereo sound tracks in theopposite direction on the same tape. By analogy to these practices, itis apparent that a motion picture presentation having zero programturnaround time could be provided by printing corresponding halves of afilm program in opposite directions on a common length of film, thefirst half of the program being shown as the film moves in one directionthrough a projector and the second half 'being shown while the filmmoves in the opposite direction simultaneously with a film rewindingoperation. It is apparent, however, that such a solution to the problemof program turnaround time requires the development and use of presentlyunavailable film printing apparatus and projection mechanism. Further,this solution to the problem of program turnaround time requires the useof film prints of limited utility. In sum, then, such a solution isprohibitively expensive. The present invention, on the other hand, usesconventional film prints.

SUMMARY OF THE INVENTION This invention provides an economic, simple,compact, reliable and efficient film entertainment system, especiallysuitable for use in commercial passenger aircraft, in which the programturnaround time is effectively zero and in which maximum use is made ofcommercially available film printing devices and projection mechanisms.The present system does not suffer from any of the disadvantagespresented by the arrangements described in the prior patents discussedabove or in the double-track, single-film arrangement considered aboveas an alternate solution to the problem of program turnaround time. Thesystem is arranged so that film is not scratched or otherwiseunnecessarily degraded during use of the system. The system may be usedrepeatedly with a single load of film to project motion pictureinformation having the same optical and sound quality as conventionalprojection systems. The system is useful with conventional film of anysize desired. The system is not sensitive to differences in filmthickness and requires manual servicing operations only when a change inthe film program is desired.

In broad terms, this invention provides a novel motion picture recordwhich includes first and second lengths of motion picture film defining,respectively, the first and second halves of a motion picture program ofdesired content, and a reel. The two lengths of film are cowound inbifilar fashion upon the reel and are disposed relative to each other sothat the head end of one film length and the tail end of the other filmlength are adjacent each other at the reel core.

The invention also provides a motion picture projection system of whichthe improved record is a component and which provides one of two reelsin the system between which the two film lengths are passed alongseparate film paths via appropriate guide means. The film lengths arecowound in bifilar fashion upon both reels. Between the reels, the filmlengths pass through projection means which includes projection lensmeans. Means are provided for driving the film lengths simultaneouslyback and forth between the reels. The projection system also includesmeans for operatively associating the projection lens means with thefilm length which moves in a forward mode through the projection meansfor display of film information carried by such film length.

As used herein with reference to the present invention, the termsprogram and motion picture program of desired content apply to a filmpresentation consisting of a single feature length motion picture withor without short subject films, and also to a film presentationcomprised of two feature length motion pictures with or without shortsubject films. It is believed that the context wherein these terms areused in the following description will make it clear which or both ofthese meanings is appropriate.

DESCRIPTION OF THE DRAWINGS The above-mentioned and other features ofthis invention are more fully set forth in the following detaileddescription of selected embodiments, including a presently preferredembodiment, of the invention, which description is presented withreference to the accompanying drawings wherein:

FIG. 1 is a schematic view of a film projection system according to thisinvention;

FIG. 2 is an enlarged elevation view showing the bifilar film reelingused in a projection system according to the invention;

FIG. 3 illustrates bifilar film winding;

FIG. 4 is a fragmentary elevation view of another projection system;

FIG. 5 is a fragmentary plan view of the projection system shown in FIG.4;

FIG. 6 is a perspective view of the projection station and filmorientation in a preferred projection system according to thisinvention;

FIG. 7 is a modification ofthe system shown in FIG. 1;

FIG. 8 is an elevation view of a portion of another projection system;

FIG. 9 is a view taken along line 99 in FIG. 8; and FIG. 10 is a view,similar to the view of FIG. 9, of still another projection system.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS Projection system 10, shownin FIG. 1, includes a pair of film storage reels 11 and 12. Each of thereels functions simultaneously, during operation of the system, both asa supply reel and as a takeup reel, as will be apparent from thefollowing description. Reel 11 is mounted to a shaft 13 of a motor 14,and reel 12 is mounted to a shaft 15 of a motor 16. Reels 11 and 12 areshown in FIG. 1 to be mounted for rotation about separate axes, but itis within the scope of the invention that the reels may be mountedcoaxially. The reels are driven at appropriate angular velocities bytheir respective drive motors. Preferably the motors per se are operatedsynchronously, each motor being coupled to the adjacent reel by astrip-tension-responsive control mechanism substantially in accord withthe disclosures of U.S. Pat. No. 3,398,914. These motors preferably arenot used to drive film through the system; instead, the reels arerotated only to supply and take up film as needed during operation ofthe system.

Two separate lengths l8 and 19 of motion picture film are engaged witheach of the reels and extend between the reels along separate filmpaths. Film lengths 18 and 19 are of essentially equal length and arewound in bifilar fashion on the reels. That is, to accomplish bifilarwinding, the film lengths are cowound on the reels so that a given turnof film length 18, for example, lies between adjacent turns of length 19about the reel core, as shown in FIG. 2. The lengths preferably arecowound on the reels in overlying or bifilar relation with theiremulsion sides facing in a common direction relative to the reel axis sothat the emulsions of the films are not in contact with each other whilethe film lengths are coiled on the reels; this arrangement prevents thefilms from sticking to each other under conditions of high humidity,protects the emulsions, and prevents degradation of the visual imagesproduced by the system during repeated displays of the informationcarried on the film lengths.

Lengths 18 and 19 define respective halves of a motion picture programof desired content. If the desired content of the program includes twofeature-length motion pictures, as may be desired where system 10 isused in a commercial passenger aircraft, each film length issufficiently long to define an entire feature film. The film lengths aredisposed in reciprocal headto-tail relation to each other between thereels. That is, if each film length is 10,000 frames in length (such alength being purely arbitrary and being mentioned only for the purposesof example), frame No. 1 of length 18 and frame No. 10,000 of length 19are adjacent each other at reel 11, for example, and frame No. 10,000 oflength 18 and frame No. 1 of length 19 are adjacent each other at reel12.

The effect of the bifilar wound, reciprocal head-to-tail arrangement offilm lengths 18 and 19 is illustrated in FIG. 3 relative to a filmlength 20. Assume that length 20 is frames long and is folded uponitself between frames 50 and 51 so that frames 50 and 51 overlie eachother and frames 1 and 100 overlie each other and so that the emulsionsurfaces of both halves of the film length face in the same direction.Assume further that the folded film length is then moved linearly past agiven point in such a manner that frames 1-50 pass serially past suchpoint; during such movement, the portion of length 20 defining framesl-50 is moving in a forward mode or direction past the point, and theportion of the film length which defines frames 51-100 is moving in areverse mode or direction past the same point. Such arrangement of filmlength 20 is directly akin to the arrangement of film lengths 18 and 19on reels 11 and 12 and to the manner in which the lengths move alongtheir separate paths between the reels.

The bifilar wound, reciprocal head-to-tail arrangement of two filmlengths of essentially equal length between two film storage reels iscommon to all projection systems according to this invention. It ispreferred, but not required, that the film lengths be wound so as tohave their emulsion sides facing in a common direction relative to thereel axes. It is also preferred that any system according to thisinvention, once threaded with film, be kept threaded; leader film may beused to maintain system threading in the event it is desired to changethe film program.

Projection means 24 are located in system along the paths of filmlengths l8 and 19 between the film reels. The projection means of system10 includes two projectors 25 and 26 associated with film lengths 18 and19, respectively. Projector 25 includes a pair of film drive sprockets27 and 28 located at opposite ends of a shuttle loop 29, a reversiblemotor 30 for rotating the sprockets and a conventional film advancemechanism (not shown), a projection lens system 31, a projection lamp32, and an audio pickup head 33 for cooperating with a sound trackcarried by film length 18; projector 26 includes correspondingcomponents 27 -33. Projection lens'system 31 and lamp 32 are alignedalong an optical axis 34 of projector 25. Lens system 31' and lamp 32 ofprojector 26 are aligned along an optical axis 35. These opti cal axesare directed to a single display screen 36 which is common to theprojection means for both film lengths.

Projection system 10 is illustrated pursuant to the assumption that filmlength 18 moves through projector 25 in a forward mode when reel drivemotors 30 and 30' are operated to transfer film through the system fromreel 11 to reel 12. Accordingly, audio pickup head 33 is located alongthe path of film length 18 between lens system 31 and reel 12, whereasaudio pickup head 33' is located along the path of film length 19between lens system 31' and reel 11.

Projectors 25 and 26 preferably are essentially conventional,commercially available motion picture projectors and are mountedbackwards (i.e., in back-to-back relation) relative to each otherbetween reels 11 and 12 to obtain the aforementioned transposition ofthe audio pickup heads relative to the optical axes of the projectors.Such reverse mounting of the projectors also places projector 26 in theproper relation to he marginal sprocket holes of film length 19, as willbe seen below.

Assume that film length 18 is wound outside" of film length 19 on reel11, as shown in FIG. 2, and both film lengths are essentially fullywound on reel 11. If the films are of equal length, i.e., contain equalnumbers of frames, and are connected to reel 11 at a common location onthe circumference of the reel core,the outer end of length 18 will bedisplaced circumferentially around the reel from the end of length 19;theamount of such displacement will be determined by the length of filmlengths 18 and 19. To avoid the use of a slack film takeup mechanism insystem 10, or to minimize the size of any slack film takeup mechanismprovided in the system, film length 18 is effectively removed from reel11 at a point which is effectively displaced around the reel from thepoint at which length 19 becomes tangent to film wound on the reel by anamount equal to the apparent difference between the lengths of film 18and 19 when both films are essentially fully wound upon reel 11. Thus,as shown in FIG. 2, film length 18 is taken from or supplied to reel 11over a roller 38 which is displaced around the reel from the locationwhere the wrap of length 19 around the reel commences. Roller 38 islocated relative to reel 11 in such a position that one-half theapparent difference in length between films l8 and 19 is adjustedadjacent reel 11 by fixed structure rather than by a movable roller orrollers located along the path of film length 18. The remaining half ofthe apparent difference in length between films 18 and 19 on reel 11 isadjusted for by a roller 39, similar to roller 38, located adjacent reel12. Thus, the apparent difference in length between strips 18 and 19 isdistributed between reels 11 and 12 in proportion to the quantities offilm wound on these reels.

Where rollers 38 and 39 are used, such rollers being mounted forrotation about fixed axes, it is important and desireable that the filmbe under essentially equal tension when initially wound onto theappropriate reel. Variations in tension between the film strips duringthe initial loading of a reel will produce a variation in the apparentlength difference between the films as wound upon the reels, and also inthe amount of film present in the system between the reels.

If film lengths l8 and 19 are taken from and supplied to the reels atcommon points on each reel, it becomes necessary to use aslack-absorbing mechanism somewhere in the path of at least film length18, for example, to accommodate the change in the apparent difference infilm strip length during operation of the system, otherwise film 18 willbecome too slack somewhere along its path or film 19 will become tootaut along its path of movement.

It was noted above that projector motors 30 and 30 are reversiblemotors. Preferably these motors are three-phase synchronous motors whichare connected in parallel to power input terminals 41 via aphase-reversing switch 42, but any type of motor may be used, theprincipal concern being to drive the films through the system at equalrates. The switch includes an actuating plunger 43 which mounts asensing roller 44 engaged with film length 18. The sensing rollernormally rides along the surface of the film adjacent a guide roller 45for film length 18. Adjacent each end of film 18, an aperture 44' isprovided through the strip. The roller detects these apertures and dropsslightly through an appropriate aperture, thereby to move plunger 43 andoperate switch 42, causing motors 30 and 30 to reverse before all filmis removed from reel 11 or reel 12, as appropriate. Switch 42 alsocontrols the direction in which reel drive motors l4 and 16 areoperated. If desired, a system shutoff switch 46 may also be controlledby plunger 43, as shown in FIG. 1, especially where each of film lengths18 and 19 defines a complete film program rather than a correspondinghalf of a complete film program. Reversal and shutoff of the system maybe controlled by only one of the film lengths since the bifilar relationof the film lengths on the reels automatically slaves gross motions ofeach film length to those of the other film length.

Projection lamps 32 and 32' are controlled so that the projector whichis operated in a forward mode during operation of the system has itsprojection lamp illuminated. In system 10, energization of lamps 32 and32' is controlled by phase reversing switch 42, as shown in FIG. 1.

The operation of system 10 may be best understood from a considerationof system 10 (FIG. 7) which includes a system shutoff switch 46 separatefrom phase-reversing switch 42 and which operates in response to thesensing of an aperture 46' positioned in film 18 adjacent the head endthereof so as not to operate the phase-reversing switch; in such a case.film lengths l8 and 19 define the first and second halves, respectively,of a complete feature length film, for example. When operation of such asystem is begun, essentially all the film in the system is stored onreel 11, and only so much film is extended to reel 12 as is necessary tomake a connection to reel 12. To initiate operation of the system, asystem start switch 95, preferably fitted with a time delay HOLDfunction to permit the reversing switch and shutoff switch sensingrollers to clear their respective film apertures, is operated. Projector25 is then operated in a forward mode (with lamp 32 illuminated) andprojector 26 is operated in a reverse mode with lamp 32' dark. Duringthis period, the information carried by film length 18 is projected upondisplay screen 36. Just before reel 11 is emptied of film, roller 44senses an aperture 44' adjacent the tail end of film length 18 andswitch 42 is operated to reverse projector motors 30 and 30' as well asreel drive motors l4 and 16. The connection of switch 42 to the reeldrive motors is not shown to simplify the illustration of FIG. 7, but issimilar to the connection of this switch to the projector motors. Whenthe projector motors are reversed, lamp 32' is illuminated and lamp 32becomes dark. The second half of the film program is then presented ondisplay screen 36 by pro jector 26 as film is transferred from reel 12back to reel 11. As the head end of film length 18 approaches reel 11,the sensing rollers of the reversing switch and the system shutoffswitch detect the apertures 44 and d6 with which they cooperate, and thesystem is turned off. The system is then in exactly the same conditionas it was when it was placed into operation.

Where each film length defines a film program which is complete initself, the system is shut off as the tail end of length 18 approachesreel 12, and also as the head end of the length approaches reel 1 1. Itis apparent, therefore, depending upon the content of the informationcarried by film lengths 18 and 19, that the invention when arranged assystem 10 can be used to show the same program during an airline flightfrom destination A to destination B as on a return flight fromdestination B to destination A, or the invention when arranged as system10 can be used to show a program during a flight from destination A todestination B which is different from the program presented during areturn flight from B to A.

Motion picture film and commercially available motion picture projectorsare cross-standardized for obvious reasons. If a length of motionpicture film is viewed from its emulsion side with the image in anygiven frame erect, film frame numbers increase proceeding from the topto the button of the length and, in the case of at least 8 mm. and 16mm. film, the film sprocket apertures are formed along the right marginof the film. Projectors are arranged so that the film is passed throughthe projector with its emulsion side disposed toward the projectionlamp, and so that the film advance mechanism of the projector engagesthe film sprocket holes adjacent a projector baseplate 47 (see FIG. 4,for example). In FIG. 3, film length 20 is viewed from its emulsionside.

It was mentioned above that projectors and 26 are essentially identical,preferably commercially available projectors which are mounted reversedrelative to each other. The reversed relative mounting of theseprojectors automatically corrects for the fact that the film sprocketholes of film length 19 are on one side of the path of length 19 andthat the sprocket holes of length 18 are on the opposite side of thepath of length 18. To correct for the inversion and transposition of theimages of film length 19 relative to those oflength 18, the lens systemof projector 26 includes a lens 48, not present in the lens system ofprojector 25, which perverts, i.e., transposes and inverts, the imagewhich otherwise would be presented by this projector on display screen36.

FIG. 4 shows a portion of a projection system 49 having two projectors5i) and 51, each of which includes a conventional film advance mechanism52 having a drive shaft 53. Each shaft 53 is coupled, via a bevel gearmechanism 54, to a reversible drive motor 55 which has its mode ofoperation controlled by phase-reversing switch 42, FIG. 4 alsoillustrates how commercially available projector mechanisms may bemounted reversed relative to each other in cooperation with film lengthsl8 and 19 to achieve the results described above.

FIG. 5 is another view of the portion of projection system 49 shown inFIG. 4. FIG. 5 shows that each of projectors 50 and 51 has a shutterplate 57 which is rotated in response to rotation of shaft 53 for theappropriate projector. Further, FIG. 5 illustrates that projectors 50and 51 may have a common projection lamp 59 as well as a commonreversible drive motor. Projectors 50 and 51 have optical axes 6i) and61, respectively, aligned essentially parallel to each other. Lamp 59 isdisposed in the plane of the optical axes behind and centrally of theprojector base plates between a pair of mirrors 62 and 63 which deflectrearward extensions of the projector optical axes to the filament oflamp 59. Preferably mirrors 62 and 63 and lamp 59 are aligned in astraight line. Lamp 59 is disposed within and coaxially of a rotatable,cylindrical, internally reflective light mask 64 having a window 65. Thelight mask is mounted on a gear 67 which cooperates with a reciprocablerack 68 connected to the armature 69 of a linear action solenoid 70. Thesolenoid has a winding 71 the energization of which is controlled byphase-reversing switch 42. The stroke of the solenoid armature and therack, and the configuration of gear 67 are selected so that mask 64 isrotated 180 about the lamp when the phase reversing switch is actuatedto alter the condition ofenergization of solenoid winding 71.

The reversing switch and the solenoid of projection system 49 arearranged so that when projector 50 is operated in its forward mode, themask is positioned to illuminate only the lens system of this projectorvia mirror 62. Conversely, when projector 51 is operated in its forwardmode, its lens system, but not the lens system of projector 50, isilluminated by lamp 59 via mirror 63. In all other significant respects,system 49 is in accord with the foregoing description and provides thesame features and advantages as does system 10 shown in FIG. 1.

FIG. 6 illustrates the significant aspects in which a projection system75, the presently preferred embodiment of this invention, differs fromsystems 10 and 49 described above; it will be understood that thedepiction of FIG. 6 is grossly simplified for clarity and ease ofillustration of the pertinent features of system 75.

Projection system 75 includes two projections 76 and 77 which arealigned substantially parallel to each other, in erect nonreversedrelation to each other, so that their optical axes 78 and 79,respectively, are directed to a common display screen. Each ofprojectors 76 and 77 preferably is a commercially available motionpicture projector and has its own reversible shutter and film advancemechanism drive motor, as is the case with system 10 described above.The projectors may have their own separate projection lamps or, ifdesired, they may share a common projection lamp as is the case insystem 49. Also, each projector includes a projection lens system 80which is identical to the lens system of the other projector; in thisrespect, system 75 is different from systems 10 and 49.

As in projection systems 10 and 49 described above, projectors 76 and 77comprise projection means located along the paths of film lengths 18 and19 between storage reels II and 12. Film lengths 118 and 19 are wound inbifilar fashion on these reels in the manner shown in FIGS. 2 and 3. Thepaths along which film lengths 18 and 19 move are arranged so that,regardless of the direction in which film is transferred between reels11 and 12, the emulsion sides of both film lengths face the projectionlamps, and the image projected on the display screen is a right-readingerect image, even though the projectors and their lens systems areidentical.

Assume that the system is operated to transfer film from reel 11 to reel12, such that projector 76 for film length 18 is operated in a forwardmode. Film 18 is moved across optical axis 78 from bottom to top (suchorientation being specified with reference to FIG. 6), and film 19 ismoved from top to bottom across optical axis 79. That is, film l8approaches projector 76 from reel 11 below optical axis 78. At theprojector, film 18 passes around a guide roller 81 and then upwardlyacross the optical axis to another guide roller 82 from which the filmmoves above the optical axis to reel 12. Film 19, however, approachesprojector 77 from above optical axis 79. At projector 77, the filmpasses around a guide roller 83, downwardly across the optical axis ofthe projector, and then around another guide roller 84 from which thefilm length moves below axis 79 to reel 12. Therefore, regardless ofwhich projector is illuminated, the image presented on the displayscreen is an erect image.

So that the image projected on the display screen by projector 77 willbe a right-reading image, and so that the sprocket holes of film length19 will be on the proper side of optical axis 79 to be engaged by thefilm advance mechanism of projector 77, film length 19 is given a axialtwist 86 in one direction between reel 11 and the projector and a 180axial twist 87 in the opposite direction between the projector and reel12.

It will be understood that twists 86 and 8'7 need not be provided infilm 19 if such film is wound on reels 11 and 12 so that its emulsionside engages the emulsion side of film 18. This expedient is notpreferred, however, for the reasons set forth above.

Projectors 76 and 77 include audio pickup heads 89 and 90, respectively,mounted for cooperation with sound tracks 91 and 92 carriedby filmlengths 18 and 19. respectively. The audio pickup devices may be eitherof the optical or the magnetic type depending upon the nature of thesound track carried by the film lengths. Audio pickup device 89 isdisposed between optical axis 78 and reel 12, whereas audio pickupdevice 90 is disposed along the path of film length 19 between opticalaxis 79 and film storage reel 11. In both cases, however, the audiopickup devices occupy the same relative posi tion within the structureof the respective projectors such that identical commercially availableprojectors may be used; the difference in the relation of the pickupunits to the film storage reels is attributable to the manner in whichfilm is passed through the respective projectors.

in each of the projection systems illustrated in FIGS. 1-7 and describedabove, the system projection means includes a projection lens assemblyfor each film path. FIGS. 8 and 9 are fragmentary views of anotherprojection system 100 which has only one projection lens assembly 101arranged along a fixed optical axis 102. As with theprojection systemsheretofore describe, system 100 includes a pair of film advancemechanisms 103 and 104 which cooperate with each of film lengths 18 and19, respectively, to drive the film lengths between a pair of filmstorage reels (not shown, but see FIG. 1, for example) upon which thefilm lengths are wound in the bifilar fashion described above. The filmadvance mechanism are operated in response to operation of a commonreversible motor 105 which is coupled to the advance mechanisms in thesame manner as is illustrated in FIG. 4 relative to system 49. The filmadvance mechanisms and motor 105 are mounted upon a support plate 107 insuch manner that the film paths adjacent the advance mechanisms are inspaced parallel coplanar relation, as shown in F168. 8 and 9. Further,the film advance mechanisms are disposed in back-to-back relation toeach other on the plate so that the image of that frame of film length18 which is adjacent a projection aperture 108 formed through thesupport plate adjacent advance mechanism 103 is perverted relative tothe image presented by that frame of film length 19 which overlies aprojection aperture 109 formed through the support plate adjacentadvance mechanism 104. In this respect, system 100 is similar toprojection systems 10, and 49 described above. The support plate ismovably supported on a pair of guide rails 110 which lie in a commonplane parallel to the common plane of the film lengths adjacent theadvance mechanisms, and which extends perpendicular to the direction inwhich the film lengths extend past the advance mechanisms (see P16. 9).

The support plate is driven along guides 110 by a drive mechanism 112which, in the exemplary arrangement shown, includes a reversible motor113, the mode of operation of which is controlled by reversing switch42. Motor 113 drives a pinion gear 114 which is engaged with a sectorgear 115 mounted for rotation about a fixed axis 116. The sector geardefines a radial slot 117 within which is loosely engaged a pin 118. Thepin is connected to one end of a connecting rod 119, the other end ofwhich is connected to the support plate. The connecting rod extendsparallel to the length of guides 110; sector gear 115 preferably lies ina plane which extends parallel to the length of the guides and isperpendicular to the common plane of the guides. Upon operation ofreversing switch 42, motor 113 is operated to drive the sector gearabout axis 116, thereby to move support plate 107 along guides 110 anamount equal to the-spacing between film lengths 18 and 19 at the filmadvance mechanisms. Upon the next operation of the reversing switch, thesector gear is driven in the opposite direction to reciprocate thesupport plate a like amount in the opposite direction.

Outwardly of each of the opposite ends of the support plate, each offilm lengths l8 and 19 pass between a pair of guide rollers 121 and 122,respectively, which are mounted for rotation about fixed axes disposedperpendicular to the support plate. A pair of guide rollers 123 aremounted to the support plate adjacent one edge thereof substantially inline with advance mechanism 103 and a similar pair of rollers 124 aremounted to the support plate adjacent its opposite edge substantially inline with the advance mechanism. Rollers 123 and 124 are rotatable aboutaxes disposed perpendicular to the support plate. Between rollers 123and advance mechanism 103, film length 18 engages a guide roller 125which is disposed for rotation about an axis parallel to the supportplate, and a similarly disposed guide roller 126 is mounted to thesupport plate between advance mechanism 103 and rollers 124. Rollers123, 124, 125 have counterparts 127, 128, 129 and 130 which define thepath of film length 19 across the support plate past film advancemechanism 104. ln view of the above-described arrangement of the rollersassociated with each of of the film lengths on the support plate, it isapparent that film length 18, for example, is given a axial twistbetween rollers 123 and and is given a second 90 axial twist betweenrollers 126 and 124, and similarly with film length 19 between rollers127 and 129 on the one hand, and rollers 130 and 128 on the other hand.The film lengths are twisted in the same direction at correspondinglocations along their film paths in view of the back-to back mounting ofthe film advance mechanisms on the support plate.

Roller pairs 121 and 122, respectively, are spaced apart along linesparallel to guides 110 an amount equal to the distance which the supportplate is moved linearly in response to operation of motor 113. As shownin FIG. 9, when the support plate is at one limit of its range ofreciprocal movement, projection aperture 109, associated with filmlength 19, is centered on optical axis 102, which axis is perpendicularto the plane of the film length at the aperture. When the support plateis at its other limit of travel, projection aperture 108 occupies theposition formerly occupied by aperture 109 and is centered on theoptical axis of stationary lens assembly 101. A projection lamp 133 isfixedly mounted in line with optical axis 102 adjacent the side of thesupport plate opposite from lens assembly 101. It is apparent,therefore, that upon operation of the'reversing switch in the mannerdescribed above relative to systems 10 and 10, support plate drivemechanism 112 is operated to cause the support plate to be moved toassociate the stationary projection lens assembly and the stationaryprojection lamp with that film length which subsequently moves in aforward mode through the projection system. That is, in the process ofreversal of the manner in which film lengths l8 and 19 are transferredbetween the pair of reels in the projection system, that film stripwhich is to be moved in a forward mode between the reels is effectivelyassociated with the projection lamp and the projection lens assembly.

It will be apparent from an examination of the structure shown in FIGS.8 and 9 in the light of the foregoing descrip tion of systems 10, 10'and 49 that a perverting lens must be associated with one or the otherof film lengths 18 or 19. Ac cordingly, a perverting lens 134 is mountedto the support plate adjacent'aperture 109 between he aperture and thelens assembly.

Film advance mechanisms 103 and 104 are arranged so that film lengths 18and 19 move in the same direction relative to support plate 107 inresponse to operation of motor 105.

Rollers 121 and 122 associated with film length 18 are located along thelength of guides 110 at positions which are midway between the positionsoccupied by rollers 123 and 124, respectively, when the support plate islocated at its opposite limits of travel along the guides; rollers 121and 122 associated with film length 19 are similarly disposed relativeto rollers 127 and 128. That is, rollers 121 for film length 18 arelocated along the perpendicular bisector along a line between rollers123 and 127, and similarly with rollers 122 for film length 18 relativeto rollers 124 and 128. Rollers 121 and 122 for film length 19 arespaced along the length of guides 110 from the corresponding rollers forfilm length 18 a distance equal to the amount of reciprocal movementafforded to the support plate. Accordingly, movement of the supportplate along guides 110 produces no change in the effective length of thefilm path between the reels for the film lengths. Preferably, motor 113is operated while film advance mechanisms 103 tion of motor 113, motor105 is not operated.

FIG. is similar to FIG. 9 and illustrates another projection system 140which bears the same relations to projection system 75 (see FIG. 6) assystem 100 bears to systems 10, 10' and 49. That is, in system 100, thefilm lengths move in the same direction past the optical axis of theprojection means of such system. In system M0, film lengths 18 and 19move in opposite directions past the single optical axis of theprojection means.

The structure of system 140, as shown in FIG. 10, is generally similarto the structure of system 100, as shown in FIG. 9, and therefore thesame reference numerals are applied to the structure of system 140 asare applied to the structure of system 100 except to the extent suchsystems are different. Thus, projection system 140 includes a pair offilm advance mechanisms 1411 and 142 which are disposed in parallelrelation to each other adjacent projection apertures 108 and 109,respectively, instead of back-to-back as is the case with advancemechanisms 103 and 104. Preferably, film advance mechanisms 141 and 142are identical and are driven in opposite directions by a reversiblemotor 143. Motor 143 drives shaft 144 to which are mounted a pair ofbelt drive pulleys 145 located coplanar with drive pulleys 146 for therespective film advance mechanisms. A drive belt 147 couples each set ofpulleys 145 and M6, the belt associated with advance mechanism 141 beingcross-looped into a figure 8 configuration, as shown in FIG. I10, sothat the film advance mechanisms are driven in opposite directions inresponse to operation of motor 143. While such is not shown in FIG. 10in order that the illustration of FIG. 10 may be simplified, system 140includes a stationary lens assembly and a stationary projection lampwhich are coaxially aligned on opposite sides of the support plate insuch position that, depending upon the state of a reversible drivemechanism for the support plate, one or the other of projectionapertures 108 or 1119 is aligned with the optical axis of the lensassembly.

In order that projection system 140 may be operated according to thesame principles which are illustrated in FIG. 6, film length 18 istwisted between rollers 123 and 125 in the direction opposite to thedirection in which film length 19 is twisted between rollers 127 and129. Similarly, film length 18 is twisted between rollers 126 and 12 1in a direction opposite to the direction of twist imparted to filmlength 19 between rollers 130 and 128. Inasmuch as film lengths 18 and19 move in opposite directions across the support plate during operationof system 140, an audio pickup device 148 for each film length ismounted to the support plate on the same side of the optical axis of thesystem. In system 100, however, an audio pickup device 135 for filmlength 18 is located adjacent roller 125, whereas an audio pickup 136device for film length 19 is located adjacent roller 130.

In each of the projection systems described above, it is desirable thatthe system, once loaded with film, not be unloaded. Thus, it isdesirable that the direction of movement of the pair of film lengthsthrough the projection system be reversed before the film lengths arecompletely removed from the reel rotating in a manner to as to pay outfilm therefrom. In order that the program to be displayed in theprojection system may be changed, it is desirable to use strips ofleader film which are permanently connected to the reels of theprojection system. That is, with reference to FIG. 1, for example, it itis desired to change the film program defined by film lengths 18 and 19,the film lengths are connected to reel 12 by strips of leader film whichare permanently secured to reel 12. The leader films have lengthsadequate to extend along the respective film paths at least to adjacentthe periphery of reel 11. Reel 11, therefore, may be removed from theprojection system by dissociating film lengths 1B and 19 from theirrespective leaders and by inserting another reel in the place of reel 11and by connecting the ends of the film lengths carried by this new reelto the adjacent ends of the leader films.

In the foregoing description of projection systems 10, 10, 49 and 75, itwas stated that the two projection lens assemblies of each system aredirected to a common display screen. It is within the scope of thisinvention that the separate lens assemblies of the projection systemsmay be directed to separate display screens, particularly where theprojection station in the system is located in the overhead area of acommercial passenger aircraft over the passenger aisle. If bothprojection lens assemblies were directed to a common screen, the screenmost probably would be located directly over the aisle some distancefrom the projection station. The presence of a display screen a such alocation either tends to impede the flow of passenger traffic along theaisle or results in interference with the display ofa motion pictureprogram as passengers move along the aisle. The dual lens system featureof systems 10, 10', 49 and 75 means that it is possible to locate adisplay screen forwardly of each lens somewhat to the side of thepassenger aisle; in such an instance only one screen need be in place asfilm is transferred in one direction between reels 11 and 12, forexample, and the other screen would be in place during movement of filmfrom reel 12 to reel 11. Especially in applications of this inventionwhere each of film lengths l8 and 19 is sufficiently long to define acomplete full-length motion picture, that screen associated with theprogram to be displayed would be lowered into place in the aircraftpassenger compartment. The other screen would be left retracted to thatpassengers could move along the aisle during display of the programwithout unduly interfering with the display. On the other hand, wherefilm lengths 18 and 19 define the first and second halves of afull-length motion picture film, the display screens could be fittedwith suitable mechanism to produce lowering of only that screen which isassociated with film moving in a forward mode through the projectionstation; upon reversal of the direction of the film lengths through theprojection station, the mechanism associated with the screens wouldautomatically lower the other screen and retract the screen used todisplay the first half of the program.

In applications of this invention where film lengths 18 and 19, forexample, define complete motion picture programs, the projection systemis capable of accommodating films initially made according to differentcinematographic processes. For example, the information carried by filmlength 18 may have been recorded on the film according to conventionalcinematographic processes such that the images recorded on the film areflat prints." On the other hand, the images recorded on film length 19might be associated with a wide screen motion picture, in which case thelens assembly associated with film length 19 would include an anamorphiclens.

In the foregoing description, reference has been made to switches whichcooperate with the film lengths for the purposes of controlling theoperation of the projection system. For the purposes of example, theseswitches have been shown as mechanical switches which include a followerroller engaged with at least one of the film lengths for sensing thepresence of an aperture formed in the film length. It will be understoodthat nonmechanical switches may also be used to advantage to obtain thedesired control functions. Such nonmechanical switches may be of themagnetic type responsive to the existence of a magnetized area at aselected location along at least one of the film lengths. Alternatively,the switch may be a photoelectric switch operated by a suitablytransparent portion of the film.

Projection systems 49, 75, and have been illustrated only in part in theaccompanying drawings in order that the drawings may be simplified. Inthe description of these systems, reference has been made to systems 10and 10', for example. Accordingly, it should be understood that each ofthe systems which are only partially graphically illustrated do includea pair of supply and takeup reels upon which a pair of film lengths arewound in reciprocal head-to-tail bifilar fashion. It should also beunderstood that the control systems illustrated in FIGS. 1 and 7 anddescribed in the foregoing explanation of systems 10 and 10' may beincorporated into systems 49, 75, 100 and 140, depending upon thecontent of the particular film program upon which it is desired that the13 projection system operate. 1515K; therefore, it should be apparentthat the features described above with respect to one particularprojection system, except to the extent that such features are thedistinguishing features for such system, may be used to advantage in anyother system without departing from the scope of this invention.

Because the two film lengths used in a projection system according tothis invention are cowound in bifilar fashion on only two reels, thefilm lengths have equal lineal velocities adjacent the respective reelsregardless of whether one film length has a greater thickness than theother. That is, the cowound bifilar arrangement of the film upon thereels renders a projection system according to this inventioninsensitive to differences in film thickness. As a result, such systemsneed not incorporate complex control mechanisms for regulatingdifferences in film velocity due to different effective diameters of thefilm supply and takeup reels; in this regard, the systems comprehendedby the invention have significant advantages over and are to bedistinguished from the arrangements shown in U.S. Pat. Nos. 1,479,078and 1,843,650 reviewed above. The film thickness insensitivity of thepresent projection systems is shown in FIG. 2. If film length 18 isthicker than film length 19, the increase in effective reel diameter foreach turn of length 18 is effectively imposed upon and reflected by thediameter of the corresponding turn of film length 19. Therefore, even ifIength IS is grossly thicker than length 19, the lengths will still haveequal linear velocities adjacent the reel as film is either payed outfrom or taken onto the reel.

Commonly owned U.S. Pat. No. 3,379,488, which also pertains to aprojection system having utility within commercial passenger aircraft,describes the projection of film information in opposite directions froma projection station. Such a projection feature may be realized from thepresent invention, in which case it may be desired to use four cowoundfilm lengths defining two duplicate film programs, the informationrecorded on the two forward moving film lengths being projected inopposite directions by separate projectors located at a commonprojection station. Also, several cinematographic processes are knownwhich require the projection of multiple recorded images upon a commonscreen or display surface. In view of these factors, this invention maybe extended, without departing from the scope thereof, to cowinding aplurality, say four film lengths, in multifilar relation on a pair ofreels, half of the lengths being disposed in head-to-tail relationrelative to the remaining lengths. During simultaneous movement of thefilms between the reels, the information recorded upon at least one ofthe film lengths is displayed by projection means located between thereels. All film lengths moving in a forward mode at any instant may besubject to display upon separate screens or upon a common screen.

It should be readily apparent to workers skilled in the art to whichthis invention pertains that the invention has utility in areas otherthan with the cabin spaces of commercial passenger aircraft. Theinvention may be used to advantage in the display of motion pictures viatelevision; in such instances, the projection means in the system may bedirected to an image orthicon tube or to a vidicon tube instead of to aconventional display screen.

In summary, then, various configurations of apparatus have beendescribed above merely for the purposes of example so that the basicteachings and utilities of the present invention may be clearlyunderstood. These structural arrangements and usages have been selectedfor presentation herein principally for the purposes of example. Also,the presently preferred embodiment of this invention has been set forthin the description which pertains to FIG. 6. Workers skilled in thetechnology to which this invention pertains will readily appreciate thatthis preferred embodiment, as well as the other illustrated embodiments,may be modified without departing from the scope of this invention.

What is claimed is:

1. A motion picture record comprising a motion picture film reel, firstand second lengths of motion picture film defining respectively firstand second halves of a motion picture film program of desired content,the films being cowound upon the reel in reciprocal head-to-tail bifilarfashion under substantially equal and substantially uniform tension.

2. A motion picture'record according to claim 1 wherein each film lengthhas an emulsion side and the lengths are cowound upon the reel withtheir emulsion sides facing in a common direction relative to the reelaxis.

3. A reeled motion picture record comprising a motion picture film reel,first and second lengths of motion picture film each having an emulsionside and defining respectively first and second halves of a motionpicture film program of desired content, the films being cowound uponthe reel in reciprocal head-to-tail bifilar fashion with their emulsionsides facing in a common direction relative to the reel axis.

4. A method of displaying a motion picture program com prising the stepsof providing first and second lengths of motion picture film whichdefine respective halves of the program,

cowinding the film lengths in reciprocal head-to-tail bifilar relationon a first reel rotatable about a stationary axis in such manner thatthe head end of the first film length and the tail end of the secondlength are located at the outer end of the bifilar coil of film on thereel,

unreeling the first and second film lengths from the reel to move thefilm lengths in one direction away from the first reel and displayingthe first half of the program simultaneously therewith, rereeling thefirst and second film lengths in said manner upon the first reel to movethe film lengths in an opposite direction toward the first reel anddisplaying the second half of the program simultaneously therewith, and

performing the unreeling and rereeling steps without moving the axis ofthe first reel.

5. A method according to claim 4 including connecting the head end ofthe first film length and the tail end of the second film length to asecond reel rotatable about a stationary axis and cowinding the filmlengths upon the second reel in reciprocal head-to-tail bifilar fashionduring unreeling of the film lengths from the first reel.

6. A method according to claim 4 including moving the first and secondfilm lengths along separate paths during the un reeling and rereelingsteps, providing a single optical axis projection means along saidpaths, and associating the projection means with the first film lengthduring the unreeling step, and associating the projection means with thesecond film length during the rereeling step.

7. A method according to claim 4 including sensing the movement of aselected portion of one of the film lengths past a selected location inthe path thereof.

8. A method according to claim 7 including commencing the rereeling stepin response to said sensing step.

9. A method according to claim 8 including defining said selectedportion of the one film length adjacent the tail end of the first filmlength.

10. A method according to claim 7 including defining the selectedlocation adjacent the periphery of the first reel.

11. A method of displaying a motion picture program comprising the stepsof providing first and second lengths of motion picture film whichdefine respective halves of the program.

cowinding the film lengths in'reciprocal head-to-tail bifilar relationon a reel in such manner that the head end of the first film length andthe tail end of the second length are located at the outer end of thebifilar coil of film on the reel,

unreeling the first and second film lengths from the reel and displayingthe first half of the program simultaneously therewith,

rereeling the first and second film lengths upon the reel and displayingthe second half of the program simultaneously therewith, and

sensing the movement ofasaected portion of the first film lengthadjacent the head end thereof past a selected location in the paththereof.

12. A method according to claim 11 including discontinuing the rereelingstep in response to said sensing step.

13. A method according to claim 11 including defining the selectedlocation adjacent the periphery of the first reel.

14. A method of displaying a motion picture program comprising the stepsof providing first and second lengths of motion picture film each ofwhich has an emulsion side and which together define respective halvesof the program,

cowinding the film length in reciprocal head-to-tial bifilar relation ona reel with the emulsion sides of the film lengths facing in a commondirection relative to the axis of the reel and arranged on the reel insuch manner that the head end of the first length and the tail end ofthe second length are located at the outer end of the bifilar coil offilm on the reel,

unreeling the first and second film lengths from the reel and displayingthe first half of the program simultaneously therewith, and

rereeling the first and second film lengths upon the reel and displayingthe second half of the program simultaneously therewith.

15. A method of displaying a motion picture program comprising the stepsof providing first and second lengths of motion picture film whichdefine respective halves of the program,

cowinding the film lengths in reciprocal head-to-tail bifilar relationon the first reel in such manner that the head end of the first filmlength and the tail end of the second length are located at the outerend of the bifilar coil of film on the reel,

unreeling the first and second film lengths from the film reel anddisplaying the first half of the program simultaneously therewith,

rereeling the first and second film lengths upon the first reel anddisplaying the second half of the program simultaneously therewith,

moving the first and second film lengths along separate paths during theunreeling and rereeling steps,

providing a single optical axis projection means along said paths, and

associating the projection means with the first film length during theunreeling step and with the second film length during the rereelingstep, the change in association of the projection means with first andsecond film lengths being effected by relative movement between theprojection means and the film paths.

16. A motion picture projection system comprising a pair of film storagereels, a pair of lengths of motion picture film defining respectivelyfirst and second halves of a film program engaged between the reels andwound upon the reels with essentially equal tension in bifilarreciprocal head-to-tail relation on the reels, reversible means fordriving the film lengths along separate film paths from one reel to theother reel and back, projection means along both film paths andincluding lens means, and means effectively associating the lens meanswith the film length moved in a forward mode through the pro jectionmeans in response to operation of the reversible means.

17. A motion picture projection system comprising a pair of film storagereels, a pair of lengths of motion picture film defining respectivelyfirst and second halves of a film program engaged between the reels andwound in bifilar reciprocal head-to-tail relation on the reels withtheir emulsion sides at each reel facing in a common direction relativeto the reel, reversible means for driving the film lengths alongseparate film paths from one reel to the other reel and back, projectionmeans along both film paths and including lens means, and meanseffectively associating the lens means with the film length moved in aforward mode through the projection means in response to operation ofthe reversible means.

18. Apparatus according to claim 17 wherein one film length is twistedrelative to the other film length between one reel and the projectionmeans and is relatively twisted between the projection means and theother reel.

19. Apparatus according to claim 18 wherein both of said twists occur inone of the film lengths.

20. Apparatus according to claim 17 wherein the lens means includes alens assembly associated with each film length.

21. Apparatus according to claim 17 wherein the lens means defines asingle optical axis along which film information carried by each filmlength is projected.

22. A motion picture projection system comprising first and second filmstorage reels each rotatable about a stationary axis, a pair of lengthsof motion picture film defining respectively first and second halves ofa film program engaged between the reels and wound in bifilar reciprocalhead-to-tail relation on the reels, reversible means for driving thefilm lengths along separate film paths from the first reel to the secondreel and back from the second reel to the first reel, projection meansalong both film paths and including lens means, and means effectivelyassociating the lens means with the film length moved in a forward modethrough the projection means in response to operation of the reversiblemeans.

23. Apparatus according to claim 22 wherein the film lengths are woundupon the reels with essentially equal tenslon.

24. Apparatus according to claim 22 wherein the film lengths are woundon the reels with their emulsion sides facing in a common direction.

25. Apparatus according to claim 22 wherein the adjacent ends of thefilm lengths are connected to the corresponding reel at substantially acommon location on the reel and the film lengths are essentially equalin length.

26. Apparatus according to claim 25 including means for guiding one filmlength to and from each of the reels so that the one length commencesits wrap around each reel at a location spaced around the circumferenceof the reel from the location at which the other film length commencesits wrap around the reel.

27. Apparatus according to claim 26 wherein the distancecircumferentially of each reel between the locations of wrapcommencement of the film lengths is effectively equal to the apparentdifference in length between the film lengths when the film lengths arewound essentially only on one of the reels.

28. Apparatus according to claim 25 including means for guiding one filmlength to and from the reels arranged so that the apparent difference inlength between the film lengths produced when both lengths are wound insaid bifilar fashion essentially only upon one of the reels isdistributed between the reels in proportion to the amount of film woundupon the respective reels.

29. A motion picture projection system comprising a pair of film storagereels, a pair of lengths of motion picture film of essentially equalelongate extent defining respectively first and second halves of a filmprogram engaged between the reels and wound with essentially equaltension in bifilar reciprocal head-to-tail relation upon the reels, theadjacent ends of the film lengths being connected to the correspondingreel at substantially a common location on the reel, means for guidingone film length to and from each of the reels so that the one lengthcommences its wrap around each reel at a location spaced around thecircumference of the reel from the location at which the other filmlength commences its wrap around the reel, reversible means for drivingthe film lengths along separate film paths from one reel to the otherreel and back, projection means along both film paths and including lensmeans, and means effectively associating the lens means with the filmlength moved in a forward mode through the projection means in responseto operation of the reversible means.

30. Apparatus according to claim 29 wherein the distancecircumferentially of each reel between the locations of wrapcommencement of the film lengths is effectively equal to the apparentdifference in lengthbe tween the film lengths when the film lengths arewound essentially only on one of the reels.

31. A motion picture projection system comprising a pair of film storagereels, a pair of lengths of motion picture film of essentially equalelongate extent defining respectively first and second halves of a filmprogram engaged between the reels and wound with essentially equaltension in bifilar reciprocal head-to-tail relation on the reels, theadjacent ends of the film lengths being connected to the correspondingreel at substantially a common location on the reel, means for guidingone film length to and from the reels arranged so that the apparentdifference in length between the film lengths produced when both lengthsare wound in said bifilar fashion essentially upon only one of the reelsis distributed between the reels in proportion to the amount of filmwound on the respective reels, reversible means for driving the filmlengths along separate film paths from one reel to the other reel andback, projection means along both film paths and including lens means,and means effectively associating the lens means with the film lengthmoved in a forward mode through the projection means in response tooperation of the reversible means.

32. A motion picture projection system comprising a pair of film storagereels, a pair of lengths of motion picture film defining respectivelyfirst and second halves of a film program engaged between the reels andwound in bifilar reciprocal head-to-tail relation on the reels,reversible means for driving the film lengths along separate film pathsfrom one reel to the other reel and back, projection means along bothfilm paths and including lens means defining a single optical axis alongwhich information carried by the film lengths is projected, and meanseffectively associating the lens means with the film length moved in aforward mode through the projection means in response to operation ofthe reversible means and including drive means operable to producerelative movement between the film paths and the optical axis, the drivemeans being arranged to cause the lens means optical axis to intersectthe path of the first film length in a first condition thereof and gocause the optical axis to intersect the path of the second film lengthin a second condition thereof.

33. Apparatus according to claim 32 including a support, wherein thereversible means includes a film advance mechanism for each film lengthmounted on the support and arranged so that the film paths at theadvance mechanisms are in spaced parallel and coplanar relation to eachother, and the drive means is operable for moving the supportperpendicularly of the film paths an amount equal to the spacing betweenthe paths.

34. Apparatus according to claim 33 including an image perverting lensmountedto the support in cooperation with one of the film paths.

35. Apparatus according to claim 33 wherein the advance mechanisms arearranged so that the film lengths are moved in the same directionrelative to the support in response to operation thereof.

36. Apparatus according to claim 33 wherein the advance mechanisms arearranged so that the film lengths move in opposite directions relativeto the support in response to opera tion thereof.

37. Apparatus according to claim 32 including guide means for guidingthe film lengths along spaced parallel paths adjacent the lens means.

38. Apparatus according to claim 37 wherein the optical axis isstationary, and the drive means is effective to move the film paths.

39. Apparatus according to claim 38 wherein the guide means is arranged.so that the effective lengths of the film paths between the reels areessentially equal to both conditions of the drive means.

40. A motion picture system comprising a pair of film storage reels,

a pair of lengths of motion picture film defining respectively first andsecond halves of a film program engaged between the reels and wound inbifilar reciprocal head-totail relation on the reels,

reversible means for driving the film lengths along separate film pathsfrom one reel to the other reel and back, projection means along bothfilm paths comprising a pair of motion picture projectors each having afilm advance mechanism, a lens system and an audio pickup device, alldisposed on a projector base plate in an arrangement identical to thearrangement of the corresponding components of the other projector, andmeans for illuminating the lens system ofthc projector associated withthe film length moved in a forward mode between the reels in response tooperation of the reversible means. 41. Apparatus according to claim 40wherein each projector includes a drive motor for the film advancemechanism thereof.

42. Apparatus according to claim 40 including a single motor for drivingthe film advance mechanisms of the projector.

43. Apparatus according to claim 40 wherein each projector includes aprojection lamp.

44. Apparatus according to claim 40 including a single projection lampcommon to the lens systems of both projectors.

45. A motion projector system comprising first and second film storagereels each rotatable about a stationary axis, a pair of lengths ofmotion picture film defining respectively first and second halves of afilm program engaged between the reels and wound in bifilar reciprocalhead-to-tail relation on the reels, reversible means for driving thefilm lengths along separate film paths from the first reel to the secondreel and back from the second reel to the first reel, projection meansalong both film paths and including a projection lens system associatedwith each film path, and means for illuminating the lens systemassociated with the film length moved in a forward mode through theprojection means in response to operation of the reversible means.

46. Apparatus according to claim 45 wherein the lens systems aredirected to a common display screen.

47. A motion picture projection system comprising a air of film storagereels, a pair of lengths of motion picture film defining respectivelyfirst and second halves of a film program engaged between the reels andwound in bifilar reciprocal head-to-tail relation on the reels,reversible means for driving the film lengths along separate film pathsfrom one reel to the other reel and back, projection means along bothfilm paths and including a projection lens system associated with eachfilm path, and means for illuminating the lens system associated withthe film length moved in a forward mode through the projection means inresponse to operation of the reversible means, one lens system per se ofthe projection means being arranged to project an image which isperverted relative to the image projected by the other lens system perse.

48. A motion picture projection system comprising a pair of film storagereels, a pair of lengths of motion picture film defining respectivelyfirst and second halves of a film program engaged between the reels andwound in bifilar reciprocal head-to-tail relation on the reels,reversible means for driving the film lengths along separate film pathsfrom one reel to the other reel and back, projection means along bothfilm paths and including a projection lens system associated with eachfilm path, and means for illuminating the lens system associated withthe film length moved in a forward mode through the projection means inresponse to operation of the reversible means, the lens systems and thefilm paths being cooperatively arranged so that during operation of thereversible means the film lengths traverse the optical axes of the lenssystems in the same direction.

49. A motiop picture projection system comprising a pair of film storagereels, a pair of lengths of motion picture film defining respectivelyfirst and second halves of a film program engaged between the reels andwound in bifilar reciprocal head-to-tail relation on the reels withtheir emulsion sides at each reel facing in a common direction relativeto the reel. reversible means for driving the film lengths alongseparate film paths from the one reel to the other reel and back,projection means along both film paths and including in association witheach film path a projection lens system each of which is essentiallyidentical to the other lens system, means for illuminating the lenssystem associated with the film length moved in a forward mode throughthe projection means in response to operation of the reversible means,one film length being twisted 180 relative to the other film lengthbetween one reel and the optical axis of the lens system associatedtherewith and being relatively twisted 180 between said optical axis andthe other reel.

50. A motion picture projection system comprising first and second filmstorage reels each rotatable about a stationary axis, a pair of lengthsof motion picture film defining respectively first and second halves ofa film program engaged between the reels and wound in bifilar reciprocalhead-to-tail relation on the reels, reversible means for driving thefilm lengths along separate film paths from the first reel to the secondreel and back from the second reel to the first reel, projection meansalong both film paths and including a projection lens system associatedwith each film path, and means for illuminating the lens systemassociated with the film length moved in a forward mode through theprojection means in response to operation of the reversible means, thelens systems and the film paths being cooperatively arranged so thatduring operation of the reversible means the film lengths traverse theoptical axes of the lens systems in opposite directions.

51. Apparatus according to claim 50 wherein the film paths are soarranged that the emulsion sides of the film lengths face in the samedirection along the optical axes of the lens systems.

52. A motion picture projection system comprising a pair of film storagereels, a pair of lengths of motion picture film defining respectivelyfirst and second halves of a film program engaged between the reels andwound in bifilar reciprocal head-to-tail relation on the reels,reversible means for driving the film lengths along separate film pathsfrom one reel to the other reel and back, reversing means forcontrolling the operational mode of the reversible means and includingmeans for generating a signal upon movement of a selected terminal partof at least one of the film lengths past a selected location in the paththereof, projection means along both film paths and including lensmeans, and means operable in response to the reversing means foreffectively associating the lens means with the film length moved in aforward mode through the projection means by the reversible means.

53. Apparatus according to claim 52 including means responsive to thesignal for discontinuing operation of the system.

54. Apparatus according to claim 52 wherein the reversible meansincludes a film advance mechanism for each film length and reversiblemotor means for driving the film advance mechanisms, and the reversingmeans is operatively coupled to the motor means for reversing the motormeans in response to said signal.

55. Apparatus according to claim 54 wherein the motor means comprises areversible drive motor for each film advance mechanism.

56. Apparatus according to claim 54 wherein the motor means consists ofa reversible motor common to both film advance mechanisms.

57. Apparatus according to claim 52 wherein the lens means includes alens system for each film path, and including projection lamp meansdisposed for illuminating the lens systems, and the effectivelyassociating means is operable for selecting for illumination by the lampmeans that lens system associated with the film length moving in aforward mode therepast.

58. Apparatus according to claim 57 wherein the projection lamp meanscomprises a projection lamp for each lens system 59. Apparatus accordingto claim 57 wherein the projection lamp means comprises a single lampcommon to both lens systems, and means responsive to said signal forshuttering light emitted by the lam between the lens systems.

60. Apparatus accor mg to claim 57 wherein the pro ection lamp meanscomprises a single lamp common to both lens systems, light mask meansdisposed between the lamp and the lens systems, and means operablealternately in response to said signal for masking light from one lenssystem and for passing light to the other lens system.

61. Apparatus for displaying information recorded on motion picture filmcomprising a pair of film storage reels each rotatable about astationary axis, a pair of lengths of motion picture film definingrespectively first and second serial portions of a film program engagedbetween the reels and wound in bifilar reciprocal head-to-tail relationon the reels, drive means for driving the film lengths along separatefilm paths between the reels for transferring said film lengths from onereel to the other, means along the film paths between the reelsoperative to display film information carried by the film length movedin a forward mode between the reels in response to operation of thedrive means, and means operative in response to transfer of essentiallyall of the film defining said lengths from the one reel to the other forreversing the drive means to transfer said film lengths from the otherreel back to the one reel and to move film in an opposite direction pastthe display means.

I Dated November 2, 1971 Patent No.

Inventor(s) Patrick Michael Powers It is certified that error appears inthe above-identified patent and that said Letters Patent are herebycorrected as shown below:

Column "I Column Column Column Column 11,

Column 12,

Column 15,

Column 17,

Column 18,

line

line

line

line

line

line

line

line

line

line

2, line 71 7, line 21 a; line 17 10, line 52-- For For

For

For

For

For

For

For

For

"mechanism" read --mechanisms--.

"button" read --bottom--.

"projections" read --projectors-.

"he" read --the-.

"tial" read --tai1--;

Before "first" and after "with", insert '--the.

For

For

For

For

"go" read --to--;

"to" read --in--.

"projector" read --picture projection-;

"air" read --pair--.

Signed and sealed this 18th day of July 1972.

' (SEAL) Attest:

EDWARD M.FLE'I'CHER,JR. Attesting Officer ROBERT GOTTSCHALK Commissionerof Patents

1. A motion picture record comprising a motion picture film reel, firstand second lengths of motion picture film defining respectively firstand second halves of a motion picture film program of desired content,the films being cowound upon the reel in reciprocal head-to-tail bifilarfashion under substantially equal and substantially uniform tension. 2.A motion picture record according to claim 1 wherein each film lengthhas an emulsion side and the lengths are cowound upon the reel withtheir emulsion sides facing in a common direction relative to the reelaxis.
 3. A reeled motion picture record comprising a motion picture filmreel, first and second lengths of motion picture film each having anemulsion side and defining respectively first and second halves of amotion picture film program of desired content, the films being cowoundupon the reel in reciprocal head-to-tail bifilar fashion with theiremulsion sides facing in a common direction relative to the reel axis.4. A method of displaying a motion picture program comprising the stepsof providing first and second lengths of motion picture film whichdefine respective halves of the program, cowinding the film lengths inreciprocal head-to-tail bifilar relation on a first reel rotatable abouta stationary axis in such manner that the head end of the first filmlength and the tail end of the second length are located at the outerend of the bifilar coil of film on the reel, unreeling the first andsecond film lengths from the reel to move the film lengths in onedirection away from the first reel and displaying the first half of theprogram simultaneously therewith, rereeling the first and second filmlengths in said manner upon the first reel to move the film lengths inan opposite direction toward the first reel and displaying the secondhalf of the program simultaneously therewith, and performing theunreeling and rereeling steps without moving the axis of the first reel.5. A method according to claim 4 including connecting the head end ofthe first film length and the tail end of the second film length to asecond reel rotatable about a stationary axis and cowinding the filmlengths upon the second reel in reciprocal head-to-tail bifilar fashionduring unreeling of the film lengths from the first reel.
 6. A methodaccording to claim 4 including moving the first and second film lengthsalong separate paths during the unreeling and rereeling steps, providinga single optical axis projection means along said paths, and associatingthe projection means with the first film length during the unreelingstep, and associating the projection means with the second film lengthduring the rereeling step.
 7. A method according to claim 4 includingsensing the movement of a selected portion of one of the film lengthspast a selected location in the path thereof.
 8. A method according toclaim 7 including commencing the rereeling step in response to saidsensing step.
 9. A method according to claim 8 including defining saidselected portion of the one film length adjacent the tail end of thefirst film length.
 10. A method according to claim 7 including definingthe selected location adjacent the periphery of the first reel.
 11. Amethod of displaying a motion picture program comprising the steps ofproviding first and second lengths of motion picture film which definerespective halves of the program, cowinding the film lengths inreciprocal head-to-tail bifilar relation on a reel in such manner thatthe head end of the first film length and the tail end of the secondlength are located at the outer end of the bifilar coil of film on thereel, unreeling the first and second film lengths from the reel anddisplaying the first half of the program simultaneously therewith,rereeling the first and second film lengths upon the reel and displayingthe second half of the program simultaneously therewith, and sensing themovement of a selected portion of the first film length adjacent thehead end thereof past a selected location in the path thereof.
 12. Amethod according to claim 11 including discontinuing the rereeling stepin response to said sensing step.
 13. A method according to claim 11including defining the selected location adjacent the periphery of thefirst reel.
 14. A method of displaying a motion picture programcomprising the steps of providing first and second lengths of motionpicture film each of which has an emulsion side and which togetherdefine respective halves of the program, cowinding the film length inreciprocal head-to-tial bifilar relation on a reel with the emulsionsides of the film lengths facing in a common direction relative to theaxis of the reel and arranged on the reel in such manner that the headend of the first length and the tail end of the second length arelocated at the outer end of the bifilar coil of film on the reel,unreeling the first and second film lengths from the reel and displayingthe first half of the program simultaneously therewith, and rereelingthe first and second film lengths upon the reel and displaying thesecond half of the program simultaneously therewith.
 15. A method ofdisplaying a motion picture program comprising the steps of providingfirst and second lengths of motion picture film which define respectivehalves of the program, cowinding the film lengths in reciprocalhead-to-tail bifilar relation on the first reel in such manner that thehead end of the first film length and the tail end of the second lengthare located at the outer end of the bifilar coil of film on the reel,unreeling the first and second film lengths from the film reel anddisplaying the first half of the program simultaneously therewith,rereeling the first and second film lengths upon the first reel anddisplaying the second half of the program simultaneously therewith,moving the first and second film lengths along separate paths during theunreeling and rereeling steps, providing a single optical axisprojection means along said paths, and associating the projection meanswith the first film length during the unreeling step and with the secondfilm length during the rereeling step, the change in association of theprojection means with first and second film lengths being effected byrelative movement between the projection means and the film paths.
 16. Amotion picture projection system comprising a pair of film storagereels, a pair of lengths of motion picture film defining respectivelyfirst and second halves of a film program engaged between the reels andwound upon the reels with essentially equal tension in bifilarreciprocal heaD-to-tail relation on the reels, reversible means fordriving the film lengths along separate film paths from one reel to theother reel and back, projection means along both film paths andincluding lens means, and means effectively associating the lens meanswith the film length moved in a forward mode through the projectionmeans in response to operation of the reversible means.
 17. A motionpicture projection system comprising a pair of film storage reels, apair of lengths of motion picture film defining respectively first andsecond halves of a film program engaged between the reels and wound inbifilar reciprocal head-to-tail relation on the reels with theiremulsion sides at each reel facing in a common direction relative to thereel, reversible means for driving the film lengths along separate filmpaths from one reel to the other reel and back, projection means alongboth film paths and including lens means, and means effectivelyassociating the lens means with the film length moved in a forward modethrough the projection means in response to operation of the reversiblemeans.
 18. Apparatus according to claim 17 wherein one film length istwisted relative to the other film length between one reel and theprojection means and is relatively twisted between the projection meansand the other reel.
 19. Apparatus according to claim 18 wherein both ofsaid twists occur in one of the film lengths.
 20. Apparatus according toclaim 17 wherein the lens means includes a lens assembly associated witheach film length.
 21. Apparatus according to claim 17 wherein the lensmeans defines a single optical axis along which film information carriedby each film length is projected.
 22. A motion picture projection systemcomprising first and second film storage reels each rotatable about astationary axis, a pair of lengths of motion picture film definingrespectively first and second halves of a film program engaged betweenthe reels and wound in bifilar reciprocal head-to-tail relation on thereels, reversible means for driving the film lengths along separate filmpaths from the first reel to the second reel and back from the secondreel to the first reel, projection means along both film paths andincluding lens means, and means effectively associating the lens meanswith the film length moved in a forward mode through the projectionmeans in response to operation of the reversible means.
 23. Apparatusaccording to claim 22 wherein the film lengths are wound upon the reelswith essentially equal tension.
 24. Apparatus according to claim 22wherein the film lengths are wound on the reels with their emulsionsides facing in a common direction.
 25. Apparatus according to claim 22wherein the adjacent ends of the film lengths are connected to thecorresponding reel at substantially a common location on the reel andthe film lengths are essentially equal in length.
 26. Apparatusaccording to claim 25 including means for guiding one film length to andfrom each of the reels so that the one length commences its wrap aroundeach reel at a location spaced around the circumference of the reel fromthe location at which the other film length commences its wrap aroundthe reel.
 27. Apparatus according to claim 26 wherein the distancecircumferentially of each reel between the locations of wrapcommencement of the film lengths is effectively equal to the apparentdifference in length between the film lengths when the film lengths arewound essentially only on one of the reels.
 28. Apparatus according toclaim 25 including means for guiding one film length to and from thereels arranged so that the apparent difference in length between thefilm lengths produced when both lengths are wound in said bifilarfashion essentially only upon one of the reels is distributed betweenthe reels in proportion to the amount of film wound upon the respectivereels.
 29. A motion picture projection system comprising a pair of filmstorage reels, a pair of lengths of motion picture film of essentiallyequal elongate extent defining respectively first and second halves of afilm program engaged between the reels and wound with essentially equaltension in bifilar reciprocal head-to-tail relation upon the reels, theadjacent ends of the film lengths being connected to the correspondingreel at substantially a common location on the reel, means for guidingone film length to and from each of the reels so that the one lengthcommences its wrap around each reel at a location spaced around thecircumference of the reel from the location at which the other filmlength commences its wrap around the reel, reversible means for drivingthe film lengths along separate film paths from one reel to the otherreel and back, projection means along both film paths and including lensmeans, and means effectively associating the lens means with the filmlength moved in a forward mode through the projection means in responseto operation of the reversible means.
 30. Apparatus according to claim29 wherein the distance circumferentially of each reel between thelocations of wrap commencement of the film lengths is effectively equalto the apparent difference in length between the film lengths when thefilm lengths are wound essentially only on one of the reels.
 31. Amotion picture projection system comprising a pair of film storagereels, a pair of lengths of motion picture film of essentially equalelongate extent defining respectively first and second halves of a filmprogram engaged between the reels and wound with essentially equaltension in bifilar reciprocal head-to-tail relation on the reels, theadjacent ends of the film lengths being connected to the correspondingreel at substantially a common location on the reel, means for guidingone film length to and from the reels arranged so that the apparentdifference in length between the film lengths produced when both lengthsare wound in said bifilar fashion essentially upon only one of the reelsis distributed between the reels in proportion to the amount of filmwound on the respective reels, reversible means for driving the filmlengths along separate film paths from one reel to the other reel andback, projection means along both film paths and including lens means,and means effectively associating the lens means with the film lengthmoved in a forward mode through the projection means in response tooperation of the reversible means.
 32. A motion picture projectionsystem comprising a pair of film storage reels, a pair of lengths ofmotion picture film defining respectively first and second halves of afilm program engaged between the reels and wound in bifilar reciprocalhead-to-tail relation on the reels, reversible means for driving thefilm lengths along separate film paths from one reel to the other reeland back, projection means along both film paths and including lensmeans defining a single optical axis along which information carried bythe film lengths is projected, and means effectively associating thelens means with the film length moved in a forward mode through theprojection means in response to operation of the reversible means andincluding drive means operable to produce relative movement between thefilm paths and the optical axis, the drive means being arranged to causethe lens means optical axis to intersect the path of the first filmlength in a first condition thereof and go cause the optical axis tointersect the path of the second film length in a second conditionthereof.
 33. Apparatus according to claim 32 including a support,wherein the reversible means includes a film advance mechanism for eachfilm length mounted on the support and arranged so that the film pathsat the advance mechanisms are in spaced parallel and coplanar relationto each other, and the drive means is operable for moving the supportperpendicularly of the film paths an amount equal to the spacing betweenthe paths.
 34. Apparatus according to claim 33 including an imagepervertiNg lens mounted to the support in cooperation with one of thefilm paths.
 35. Apparatus according to claim 33 wherein the advancemechanisms are arranged so that the film lengths are moved in the samedirection relative to the support in response to operation thereof. 36.Apparatus according to claim 33 wherein the advance mechanisms arearranged so that the film lengths move in opposite directions relativeto the support in response to operation thereof.
 37. Apparatus accordingto claim 32 including guide means for guiding the film lengths alongspaced parallel paths adjacent the lens means.
 38. Apparatus accordingto claim 37 wherein the optical axis is stationary, and the drive meansis effective to move the film paths.
 39. Apparatus according to claim 38wherein the guide means is arranged so that the effective lengths of thefilm paths between the reels are essentially equal to both conditions ofthe drive means.
 40. A motion picture system comprising a pair of filmstorage reels, a pair of lengths of motion picture film definingrespectively first and second halves of a film program engaged betweenthe reels and wound in bifilar reciprocal head-to-tail relation on thereels, reversible means for driving the film lengths along separate filmpaths from one reel to the other reel and back, projection means alongboth film paths comprising a pair of motion picture projectors eachhaving a film advance mechanism, a lens system and an audio pickupdevice, all disposed on a projector base plate in an arrangementidentical to the arrangement of the corresponding components of theother projector, and means for illuminating the lens system of theprojector associated with the film length moved in a forward modebetween the reels in response to operation of the reversible means. 41.Apparatus according to claim 40 wherein each projector includes a drivemotor for the film advance mechanism thereof.
 42. Apparatus according toclaim 40 including a single motor for driving the film advancemechanisms of the projector.
 43. Apparatus according to claim 40 whereineach projector includes a projection lamp.
 44. Apparatus according toclaim 40 including a single projection lamp common to the lens systemsof both projectors.
 45. A motion projector system comprising first andsecond film storage reels each rotatable about a stationary axis, a pairof lengths of motion picture film defining respectively first and secondhalves of a film program engaged between the reels and wound in bifilarreciprocal head-to-tail relation on the reels, reversible means fordriving the film lengths along separate film paths from the first reelto the second reel and back from the second reel to the first reel,projection means along both film paths and including a projection lenssystem associated with each film path, and means for illuminating thelens system associated with the film length moved in a forward modethrough the projection means in response to operation of the reversiblemeans.
 46. Apparatus according to claim 45 wherein the lens systems aredirected to a common display screen.
 47. A motion picture projectionsystem comprising a air of film storage reels, a pair of lengths ofmotion picture film defining respectively first and second halves of afilm program engaged between the reels and wound in bifilar reciprocalhead-to-tail relation on the reels, reversible means for driving thefilm lengths along separate film paths from one reel to the other reeland back, projection means along both film paths and including aprojection lens system associated with each film path, and means forilluminating the lens system associated with the film length moved in aforward mode through the projection means in response to operation ofthe reversible means, one lens system per se of the projection meansbeing arranged to project an image which is perverted relative to theimage projected by the other lens system per se.
 48. A motion pictuReprojection system comprising a pair of film storage reels, a pair oflengths of motion picture film defining respectively first and secondhalves of a film program engaged between the reels and wound in bifilarreciprocal head-to-tail relation on the reels, reversible means fordriving the film lengths along separate film paths from one reel to theother reel and back, projection means along both film paths andincluding a projection lens system associated with each film path, andmeans for illuminating the lens system associated with the film lengthmoved in a forward mode through the projection means in response tooperation of the reversible means, the lens systems and the film pathsbeing cooperatively arranged so that during operation of the reversiblemeans the film lengths traverse the optical axes of the lens systems inthe same direction.
 49. A motion picture projection system comprising apair of film storage reels, a pair of lengths of motion picture filmdefining respectively first and second halves of a film program engagedbetween the reels and wound in bifilar reciprocal head-to-tail relationon the reels with their emulsion sides at each reel facing in a commondirection relative to the reel, reversible means for driving the filmlengths along separate film paths from the one reel to the other reeland back, projection means along both film paths and including inassociation with each film path a projection lens system each of whichis essentially identical to the other lens system, means forilluminating the lens system associated with the film length moved in aforward mode through the projection means in response to operation ofthe reversible means, one film length being twisted 180* relative to theother film length between one reel and the optical axis of the lenssystem associated therewith and being relatively twisted 180* betweensaid optical axis and the other reel.
 50. A motion picture projectionsystem comprising first and second film storage reels each rotatableabout a stationary axis, a pair of lengths of motion picture filmdefining respectively first and second halves of a film program engagedbetween the reels and wound in bifilar reciprocal head-to-tail relationon the reels, reversible means for driving the film lengths alongseparate film paths from the first reel to the second reel and back fromthe second reel to the first reel, projection means along both filmpaths and including a projection lens system associated with each filmpath, and means for illuminating the lens system associated with thefilm length moved in a forward mode through the projection means inresponse to operation of the reversible means, the lens systems and thefilm paths being cooperatively arranged so that during operation of thereversible means the film lengths traverse the optical axes of the lenssystems in opposite directions.
 51. Apparatus according to claim 50wherein the film paths are so arranged that the emulsion sides of thefilm lengths face in the same direction along the optical axes of thelens systems.
 52. A motion picture projection system comprising a pairof film storage reels, a pair of lengths of motion picture film definingrespectively first and second halves of a film program engaged betweenthe reels and wound in bifilar reciprocal head-to-tail relation on thereels, reversible means for driving the film lengths along separate filmpaths from one reel to the other reel and back, reversing means forcontrolling the operational mode of the reversible means and includingmeans for generating a signal upon movement of a selected terminal partof at least one of the film lengths past a selected location in the paththereof, projection means along both film paths and including lensmeans, and means operable in response to the reversing means foreffectively associating the lens means with the film length moved in aforward mode through the projection means by the reversible means. 53.Apparatus accordiNg to claim 52 including means responsive to the signalfor discontinuing operation of the system.
 54. Apparatus according toclaim 52 wherein the reversible means includes a film advance mechanismfor each film length and reversible motor means for driving the filmadvance mechanisms, and the reversing means is operatively coupled tothe motor means for reversing the motor means in response to saidsignal.
 55. Apparatus according to claim 54 wherein the motor meanscomprises a reversible drive motor for each film advance mechanism. 56.Apparatus according to claim 54 wherein the motor means consists of areversible motor common to both film advance mechanisms.
 57. Apparatusaccording to claim 52 wherein the lens means includes a lens system foreach film path, and including projection lamp means disposed forilluminating the lens systems, and the effectively associating means isoperable for selecting for illumination by the lamp means that lenssystem associated with the film length moving in a forward modetherepast.
 58. Apparatus according to claim 57 wherein the projectionlamp means comprises a projection lamp for each lens system. 59.Apparatus according to claim 57 wherein the projection lamp meanscomprises a single lamp common to both lens systems, and meansresponsive to said signal for shuttering light emitted by the lampbetween the lens systems.
 60. Apparatus according to claim 57 whereinthe projection lamp means comprises a single lamp common to both lenssystems, light mask means disposed between the lamp and the lenssystems, and means operable alternately in response to said signal formasking light from one lens system and for passing light to the otherlens system.
 61. Apparatus for displaying information recorded on motionpicture film comprising a pair of film storage reels each rotatableabout a stationary axis, a pair of lengths of motion picture filmdefining respectively first and second serial portions of a film programengaged between the reels and wound in bifilar reciprocal head-to-tailrelation on the reels, drive means for driving the film lengths alongseparate film paths between the reels for transferring said film lengthsfrom one reel to the other, means along the film paths between the reelsoperative to display film information carried by the film length movedin a forward mode between the reels in response to operation of thedrive means, and means operative in response to transfer of essentiallyall of the film defining said lengths from the one reel to the other forreversing the drive means to transfer said film lengths from the otherreel back to the one reel and to move film in an opposite direction pastthe display means.